(I am only 3 episodes into The Boys, nor have I read the comics, so I don't know if this is answered later on).
In The Boys (2019 TV series) it seems that the world has an immense number of superheroes, even to the point that Vought desires to have a Supe in basically every small town/city across the US. In the actual crime fighting situations we have seen to date the Supes are only taking down normal human criminals.
So given the wide extent of whatever mutation turns a human into a Supe, why are there apparently no super villains in this universe?
This is especially odd given that:
A lot of the Supes we have encountered so far are immoral/unethical - attributes of your typical super villain. (So perhaps you could argue that they are their own super villains?!)
And as an explicit Supe example
A-Train's FWB, Popclaw is so down on her luck (after being a well recognized Supe in the past) that she can't even pay the rent on her apartment, and is also basically a junkie (and dealer to A-Train). So it wouldn't be much of a step for her to turn criminal.
Note that by super villain I mean doing things that super villains generally do - holding entire cities to ransom, stealing super weapons etc and not the normal human crimes of theft, bank robbery and murder etc.